Settable compositions comprising unexpanded perlite and methods of cementing in subterranean formations

ABSTRACT

An embodiment of the present invention comprises a method of cementing comprising: placing a settable composition into a well bore, the settable composition comprising unexpanded perlite, cement kiln dust, and water; and allowing the settable composition to set. Another embodiment of the present invention comprises a method of cementing comprising: placing a settable composition into a well bore, the settable composition comprising ground unexpanded perlite, Portland cement interground with pumicite, and water; and allowing the settable composition to set. Yet another embodiment of the present invention comprises a settable composition comprising: ground unexpanded perlite; cement kiln dust; and water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is divisional of U.S. patent application Ser. No.13/606,098, filed on Sep. 7, 2012, which is a divisional of U.S. patentapplication Ser. No. 12/975,196, filed on Dec. 21, 2010, which is acontinuation-in-part of U.S. patent application Ser. No. 12/821,412,filed on Jun. 23, 2010, which is a continuation-in-part of U.S. patentapplication Ser. No. 12/606,381, filed on Oct. 27, 2009, issued as U.S.Pat. No. 7,743,828, which is a continuation-in-part of U.S. patentapplication Ser. No. 12/420,630, filed on Apr. 8, 2009, issued as U.S.Pat. No. 7,631,692, which is a continuation-in-part of U.S. patentapplication Ser. No. 12/349,676, filed on Jan. 7, 2009, issued as U.S.Pat. No. 7,674,332, which is a divisional of U.S. patent applicationSer. No. 12/034,886, filed on Feb. 21, 2008, issued as U.S. Pat. No.7,478,675, which is a continuation-in-part of U.S. patent applicationSer. No. 11/223,669, filed Sep. 9, 2005, issued as U.S. Pat. No.7,445,669, the entire disclosures of which are incorporated herein byreference.

BACKGROUND

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to methods and compositions thatcomprise unexpanded perlite with cement kiln dust (“CKD”), pumicite, ora combination thereof.

In cementing methods, such as well construction and remedial cementing,settable compositions are commonly utilized. As used herein, the term“settable composition” refers to a composition(s) that hydraulicallysets or otherwise develops compressive strength. Settable compositionsmay be used in primary cementing operations whereby pipe strings, suchas casing and liners, are cemented in well bores. In performing primarycementing, a settable composition may be pumped into an annulus betweena subterranean formation and the pipe string disposed in thesubterranean formation. The settable composition should set in theannulus, thereby forming an annular sheath of hardened cement (e.g., acement sheath) that should support and position the pipe string in thewell bore and bond the exterior surface of the pipe string to the wallsof the well bore. Settable compositions also may be used in remedialcementing methods, such as the placement of cement plugs, and in squeezecementing for sealing voids in a pipe string, cement sheath, gravelpack, formation, and the like.

SUMMARY

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to compositions and methods thatinclude unexpanded perlite, CKD, and/or pumicite.

An embodiment of the present invention comprises a method of cementingcomprising: placing a settable composition into a well bore, thesettable composition comprising unexpanded perlite, cement kiln dust,and water; and allowing the settable composition to set.

Another embodiment of the present invention comprises a method ofcementing comprising: placing a settable composition into a well bore,the settable composition comprising ground unexpanded perlite, Portlandcement interground with pumicite, and water; and allowing the settablecomposition to set.

Yet another embodiment of the present invention comprises a settablecomposition comprising: ground unexpanded perlite; cement kiln dust; andwater.

The features and advantages of the present invention will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to methods and compositions thatcomprise unexpanded perlite with CKD, pumicite, or a combinationthereof. There may be several potential advantages to the methods andcompositions of the present invention, only some of which may be alludedto herein. One of the many potential advantages of embodiments of thepresent invention is that the inclusion of the unexpanded perlite inembodiments of the settable composition may increase the compressivestrength of the settable composition after setting. Another potentialadvantage of embodiments of the present invention is that the CKD,unexpanded perlite, pumicite, or a combination thereof may be used toreduce the amount of a higher cost component, such as Portland cement,resulting in a more economical settable composition. Yet anotherpotential advantage of embodiments of the present invention is thatreduction of the amount of Portland cement can reduce the carbonfootprint of the cementing operation.

Embodiments of the settable compositions of the present invention maycomprise unexpanded perlite with CKD, pumicite or a combination thereof.Embodiments of the settable compositions further may comprise water, forexample, in an amount sufficient to form a pumpable slurry. In oneparticular embodiment, the settable composition may comprise acementitious component that comprises unexpanded perlite and CKD. Inanother embodiment, the settable composition may comprise a cementitiouscomponent that comprises unexpanded perlite, CKD, and pumicite. In yetanother embodiment, the settable composition may comprise a cementitiouscomponent that comprises unexpanded perlite and pumicite. In yet anotherembodiment, the settable composition may comprise a cementitiouscomponent that comprises unexpanded perlite and pumicite intergroundwith a hydraulic cement. In yet another embodiment, the settablecomposition may comprise a cementitious component that comprisesunexpanded perlite interground with a hydraulic cement. Optionally, thesettable compositions described herein may comprise lime. In oneparticular embodiment, the settable composition comprises a cementitiouscomponent that comprises unexpanded perlite, CKD, pumicite, and/or lime.Other optional additives may also be included in embodiments of thesettable compositions as desired, including, but not limited to, flyash, slag cement, metakaolin, shale, zeolite, combinations thereof, andthe like. Embodiments of the settable compositions may be foamed and/orextended as desired by those of ordinary skill in the art.

The settable compositions of the present invention should have a densitysuitable for a particular application as desired by those of ordinaryskill in the art, with the benefit of this disclosure. In someembodiments, the settable compositions may have a density in the rangeof from about 8 pounds per gallon (“ppg”) to about 16 ppg. In otherembodiments, the settable compositions may be foamed to a density in therange of from about 8 ppg to about 13 ppg.

Embodiments of the settable compositions generally may compriseunexpanded perlite. Perlite is an ore and generally refers to anaturally occurring volcanic, amorphous siliceous rock comprising mostlysilicon dioxide and aluminum oxide. A characteristic of perlite is thatit may expand to form a cellular, high-porosity particle or hollowsphere containing multi-cellular cores when exposed to high temperaturesdue to the sudden vaporization of water within the perlite. The expandedperlite may be used as a density-reducing additive for makinglightweight settable compositions.

It has recently been discovered the addition of unexpanded perlite tosettable compositions comprising CKD and/or pumicite may provideunexpected increases in compressive strengths. In accordance withembodiments of the present invention, the unexpanded perlite may be usedto increase the compressive strength of settable compositions comprisingCKD and/or pumicite. In addition, unexpanded perlite can increase thecompressive strength of settable compositions comprising Portlandcement. It is believed that the unexpanded perlite may be particularlysuited for use at elevated well bore temperatures in accordance withembodiments of the present invention, such as at temperatures greaterthan about 80° F., alternatively greater than about 120° F., andalternatively greater than about 140° F.

In one embodiment, unexpanded perlite may be used, among other things,to replace higher cost cementitious components, such as Portland cement,resulting in more economical settable compositions. In addition,substitution of the Portland cement for the unexpanded perlite shouldresult in a settable composition with a reduced carbon footprint.

In present embodiments, the unexpanded perlite can be ground to any sizesuitable for use in cementing operations. In an embodiment, theunexpanded perlite is ground to a mean particle size of about 1 micronto about 400 microns, alternatively, about 1 micron to about 100 micronsand, alternatively, about 1 micron to about 25 microns. The meanparticle size corresponds to d50 values as measured by commerciallyavailable particle size analyzers such as those manufactured by MalvernInstruments, Worcestershire, United Kingdom. In another embodiment, theunexpanded perlite has a particle size distribution of about 1 micron toabout 1,000 microns with a mean particle size of about 1 micron to about100 microns. The particle size distribution corresponds to the maximumand minimum sizes allowed in the distribution. An example of a suitableground unexpanded perlite is available from Hess Pumice Products, Inc.,Malad City, Id., under the tradename IM-325 with a mesh size of 325.

In one particular embodiment, the unexpanded perlite can be intergroundwith hydraulic cement, such as Portland cement, for example. In anotherembodiment, the unexpanded perlite can be interground with hydrauliccement and pumicite. In an embodiment, the ground perlite/cement mixturecontains hydraulic cement in an amount of about 25% to about 75% byweight of the mixture and unexpanded perlite in an amount of about 25%to about 75% by weight of the mixture. In one embodiment, the hydrauliccement may be a Portland cement classified as ASTM Type V cement. Inaccordance with embodiments, the hydraulic cement and unexpanded perlitemay be combined and ground to any size suitable for use in cementingoperations. In another embodiment, the hydraulic cement and unexpandedperlite may be ground prior to combination. In an embodiment, the groundperlite/cement mixture has a mean particle size of about 0.1 microns toabout 400 microns, alternatively, about 0.5 microns to about 50 microns,and alternatively, about 0.5 microns to about 10 microns. The meanparticle size corresponds to d50 values as measured by commerciallyavailable particle size analyzers such as those manufactured by MalvernInstruments, Worcestershire, United Kingdom.

The unexpanded perlite may be included in the settable compositions inan amount sufficient to provide the desired compressive strength,density, cost reduction, and/or reduced carbon footprint. In someembodiments, the unexpanded perlite may be present in the settablecompositions of the present invention in an amount in the range of fromabout 1% to about 75% by weight of cementitious components. Cementitiouscomponents include those components or combinations of components of thesettable compositions that hydraulically set, or otherwise harden, todevelop compressive strength, including, for example, unexpandedperlite, CKD, fly ash, pumicite, slag, lime, shale, and the like. Theunexpanded perlite may be present, in certain embodiments, in an amountof about 5%, about 10%, about 15%, about 20%, about 25%, about 30%,about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about65%, or about 70%. In one embodiment, the unexpanded perlite may bepresent in the settable compositions in an amount in the range of fromabout 5% to about 50% by weight of cementitious components. In anotherembodiment, the unexpanded perlite may be present in an amount in therange of from about 10% to about 40% by weight of cementitiouscomponents. In yet another embodiment, the unexpanded perlite may bepresent in an amount in the range of from about 20% to about 30% byweight of cementitious components. One of ordinary skill in the art,with the benefit of this disclosure, will recognize the appropriateamount of unexpanded perlite to include for a chosen application.

Embodiments of the settable compositions generally may comprise CKD.Usually, large quantities of CKD are collected in the production ofcement that are commonly disposed of as waste. Disposal of the waste CKDcan add undesirable costs to the manufacture of the cement, as well asthe environmental concerns associated with its disposal. The chemicalanalysis of CKD from various cement manufactures varies depending on anumber of factors, including the particular kiln feed, the efficienciesof the cement production operation, and the associated dust collectionsystems. CKD generally may comprise a variety of oxides, such as SiO₂,Al₂O₃, Fe₂O₃, CaO, MgO, SO₃, Na₂O, and K₂O.

The CKD generally may exhibit cementitious properties, in that it mayset and harden in the presence of water. In accordance with embodimentsof the present invention, the CKD may be used, among other things, toreplace higher cost cementitious components, such as Portland cement,resulting in more economical settable compositions. In addition,substitution of the Portland cement for the CKD can result in a settablecomposition with a reduced carbon footprint.

The CKD may be included in the settable compositions in an amountsufficient to provide the desired compressive strength, density, costreduction, and/or reduced carbon footprint. In some embodiments, the CKDmay be present in the settable compositions of the present invention inan amount in the range of from about 1% to about 95% by weight ofcementitious components. The CKD may be present, in certain embodiments,in an amount of about 5%, about 10%, about 15%, about 20%, about 25%,about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about60%, about 65%, about 70%, about 75%, about 80%, or about 90%. In oneembodiment, the CKD may be present in the settable compositions in anamount in the range of from about 5% to about 95% by weight ofcementitious components. In another embodiment, the CKD may be presentin an amount in the range of from about 50% to about 90% by weight ofcementitious components. In yet another embodiment, the CKD may bepresent in an amount in the range of from about 60% to about 80% byweight of cementitious components. One of ordinary skill in the art,with the benefit of this disclosure, will recognize the appropriateamount of CKD to include for a chosen application.

Embodiments of the settable compositions further may comprise pumicite.Generally, pumicite is a volcanic rock that exhibits cementitiousproperties, in that it may set and harden in the presence of hydratedlime and water. Hydrated lime may be used in combination with thepumicite, for example, to provide sufficient calcium ions for thepumicite to set. In accordance with embodiments of the presentinvention, the pumicite may be used, among other things, to replacehigher cost cementitious components, such as Portland cement, resultingin more economical settable compositions. As previously mentioned,replacement of the Portland cement should also result in a settablecomposition with a reduced carbon footprint.

Where present, the pumicite may be included in an amount sufficient toprovide the desired compressive strength, density, cost reduction and/orreduced carbon footprint for a particular application. In someembodiments, the pumicite may be present in the settable compositions ofthe present invention in an amount in the range of from about 1% toabout 95% by weight of cementitious components. For example, thepumicite may be present in an amount of about 5%, about 10%, about 15%,about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%,or about 90%. In one embodiment, the pumicite may be present in thesettable compositions of the present invention in an amount in the rangeof from about 5% to about 95% by weight of cementitious components. Inanother embodiment, the pumicite may be present in an amount in therange of from about 5% to about 80% by weight of cementitiouscomponents. In yet another embodiment, the pumicite may be present in anamount in the range of from about 10% to about 50% by weight ofcementitious components. In yet another embodiment, the pumicite may bepresent in an amount in the range of from about 25% to about 50% byweight of cementitious components. One of ordinary skill in the art,with the benefit of this disclosure, will recognize the appropriateamount of the pumicite to include for a chosen application.

The water that may be used in embodiments of the settable compositionsinclude, for example, freshwater, saltwater (e.g., water containing oneor more salts dissolved therein), brine (e.g., saturated saltwaterproduced from subterranean formations), seawater, or combinationsthereof. Generally, the water may be from any source, provided that thewater does not contain an excess of compounds that may undesirablyaffect other components in the settable composition. In someembodiments, the water may be included in an amount sufficient to form apumpable slurry. In some embodiments, the water may be included in thesettable compositions of the present invention in an amount in the rangeof about 40% to about 200% by weight of cementitious components. In someembodiments, the water may be included in an amount in the range ofabout 40% to about 150% by weight of cementitious components. One ofordinary skill in the art, with the benefit of this disclosure, willrecognize the appropriate amount of water to include for a chosenapplication.

Embodiments of the settable compositions further may comprise lime. Incertain embodiments, the lime may be hydrated lime. The lime may beincluded in embodiments of the settable compositions, for example, toform a hydraulic composition with other components of the settablecompositions, such as the pumicite, fly ash, slag, and/or shale. Wherepresent, the lime may be included in the settable compositions in anamount sufficient for a particular application. In some embodiments, thelime may be present in an amount in the range of from about 1% to about40% by weight of cementitious components. For example, the lime may bepresent in an amount of about 5%, about 10%, about 15%, about 20%, about25%, about 30%, or about 35%. In one embodiment, the lime may be presentin an amount in the range of from about 5% to about 20% by weight ofcementitious components. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of thelime to include for a chosen application.

It should be understood that use of Portland cement in embodiments ofthe settable compositions can be reduced or even eliminated to provide,for example, the desired cost savings and/or reduced carbon footprint.Accordingly, embodiments of the settable compositions of the presentinvention may comprise Portland cement in an amount of 0% to about 75%.For example, the Portland cement may be present in an amount of about1%, 5%, about 10%, about 15%, about 20%, about 24%, about 25%, about30%, about 35%, about 40%, about 50%, about 55%, about 60%, about 65%,or about 70%. In an embodiment, the Portland cement may be present in anamount in the range of from about 0% to about 20%. In anotherembodiment, the Portland cement may be present in an amount in the rangeof from about 0% to about 10%. In yet another embodiment, the settablecompositions may be essentially free of Portland cement. As used herein,the term “essentially free” means less than about 1% by weight ofcementitious components. In certain embodiments, the settablecomposition may contain Portland cement in an amount less than about0.1% by weight of cementitious components and, alternatively, less thanabout 0.01% by weight of cementitious components. By way of example, thesettable composition, in certain embodiments, may be free of Portlandcement, in that the settable composition contains no Portland cement.

The Portland cements include those classified as Classes A, C, G, and Hcements according to American Petroleum Institute, API Specification forMaterials and Testing for Well Cements, API Specification 10, Fifth Ed.,Jul. 1, 1990. In addition, the Portland cements include those classifiedas ASTM Type I, II, or III.

One example of a suitable hydraulic cement comprises a mixture ofPortland cement and pumicite. In an embodiment, the cement/pumicitemixture contains Portland cement in an amount of about 25% to about 75%by weight of the mixture and pumicite in an amount of about 25% to about75% by weight of the mixture. In an embodiment, the cement/pumicitemixture contains about 40% Portland cement by weight and about 60%pumicite by weight. In an embodiment, the hydraulic cement may comprisePortland cement interground with pumicite. In one embodiment, thePortland cement may be classified as ASTM Type V cement. In accordancewith embodiments, the Portland cement and pumicite may be combined andground to any size suitable for use in cementing operations. In anotherembodiment, the Portland cement and pumicite may be ground prior tocombination. In an embodiment, the cement/pumicite mixture of Portlandcement and pumicite has a mean particle size of about 0.1 microns toabout 400 microns, alternatively, about 0.5 microns to about 50 microns,and alternatively, about 0.5 microns to about 10 microns. The meanparticle size corresponds to d50 values as measured by commerciallyavailable particle size analyzers such as those manufactured by MalvernInstruments, Worcestershire, United Kingdom. An example of a suitablecement/pumicite mixture is available from Halliburton Energy Services,Inc., under the trade name FineCem™ 925 cement.

It is believed that hydraulic cement interground with pumicite when usedin a settable composition in combination with unexpanded perlite mayprovided synergistic effects. For example, it is believed that thecombination of unexpanded perlite and the cement/pumicite mixture mayprovide significantly higher compressive strength, particularly atelevated well bore temperatures. Accordingly, the combination ofunexpanded perlite and the cement/pumicite mixture may be particularlysuited for use in settable compositions at elevated well boretemperatures, such as at temperatures greater than about 80° F.,alternatively greater than about 120° F., and alternatively greater thanabout 140° F.

Embodiments of the settable compositions further may comprise fly ash. Avariety of fly ashes may be suitable, including fly ash classified asClass C and Class F fly ash according to American Petroleum Institute,API Specification for Materials and Testing for Well Cements, APISpecification 10, Fifth Ed., Jul. 1, 1990. Class C fly ash comprisesboth silica and lime so that, when mixed with water, it should set toform a hardened mass. Class F fly ash generally does not containsufficient lime, so an additional source of calcium ions is typicallyrequired for the Class F fly ash to form a hydraulic composition. Insome embodiments, lime may be mixed with Class F fly ash in an amount inthe range of about 0.1% to about 25% by weight of the fly ash. In someinstances, the lime may be hydrated lime. Suitable examples of fly ashinclude, but are not limited to, POZMIX® A cement additive, commerciallyavailable from Halliburton Energy Services, Inc.

Where present, the fly ash generally may be included in the settablecompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the fly ash may bepresent in the settable compositions of the present invention in anamount in the range of about 1% to about 75% by weight of cementitiouscomponents. In some embodiments, the fly ash may be present in an amountin the range of about 10% to about 60% by weight of cementitiouscomponents. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of the fly ash toinclude for a chosen application.

Embodiments of the settable compositions further may comprise a slagcement. In some embodiments, a slag cement that may be suitable for usemay comprise slag. Slag generally does not contain sufficient basicmaterial, so slag cement further may comprise a base to produce ahydraulic composition that may react with water to set to form ahardened mass. Examples of suitable sources of bases include, but arenot limited to, sodium hydroxide, sodium bicarbonate, sodium carbonate,lime, and combinations thereof.

Where present, the slag cement generally may be included in the settablecompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the slag cement maybe present in the settable compositions of the present invention in anamount in the range of about 1% to about 75% by weight of cementitiouscomponents. In some embodiments, the slag cement may be present in anamount in the range of about 5% to about 50% by weight of cementitiouscomponents. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of the slag cement toinclude for a chosen application.

Embodiments of the settable compositions further may comprisemetakaolin. Generally, metakaolin is a white pozzolan that may beprepared by heating kaolin clay, for example, to temperatures in therange of about 600° C. to about 800° C. In some embodiments, themetakaolin may be present in the settable compositions of the presentinvention in an amount in the range of about 1% to about 75% by weightof cementitious components. In some embodiments, the metakaolin may bepresent in an amount in the range of about 10% to about 50% by weight ofcementitious components. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of themetakaolin to include for a chosen application.

Embodiments of the settable compositions further may comprise shale.Among other things, shale included in the settable compositions mayreact with excess lime to form a suitable cementing material, forexample, calcium silicate hydrate. A variety of shales may be suitable,including those comprising silicon, aluminum, calcium, and/or magnesium.An example of a suitable shale comprises vitrified shale. Suitableexamples of vitrified shale include, but are not limited to,PRESSUR-SEAL FINE LCM material and PRESSUR-SEAL COARSE LCM material,which are commercially available from TXI Energy Services, Inc.Generally, the shale may have any particle size distribution as desiredfor a particular application. In certain embodiments, the shale may havea particle size distribution in the range of about 37 micrometers toabout 4,750 micrometers.

Where present, the shale may be included in the settable compositions ofthe present invention in an amount sufficient to provide the desiredcompressive strength, density, and/or cost. In some embodiments, theshale may be present in the settable compositions of the presentinvention in an amount in the range of about 1% to about 75% by weightof cementitious components. In some embodiments, the shale may bepresent in an amount in the range of about 10% to about 35% by weight ofcementitious components. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of theshale to include for a chosen application.

Embodiments of the settable compositions further may comprise zeolite.Zeolites generally are porous alumino-silicate minerals that may beeither a natural or synthetic material. Synthetic zeolites are based onthe same type of structural cell as natural zeolites, and may comprisealuminosilicate hydrates. As used herein, the term “zeolite” refers toall natural and synthetic forms of zeolite. Examples of suitablezeolites are described in more detail in U.S. Pat. No. 7,445,669. Anexample of a suitable source of zeolite is available from the C2CZeolite Corporation of Calgary, Canada. In some embodiments, the zeolitemay be present in the settable compositions of the present invention inan amount in the range of about 1% to about 65% by weight ofcementitious components. In certain embodiments, the zeolite may bepresent in an amount in the range of about 10% to about 40% by weight ofcementitious components. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of thezeolite to include for a chosen application.

Embodiments of the settable compositions further may comprise a setretarding additive. As used herein, the term “set retarding additive”refers to an additive that retards the setting of the settablecompositions of the present invention. Examples of suitable setretarding additives include, but are not limited to, ammonium, alkalimetals, alkaline earth metals, metal salts of sulfoalkylated lignins,organic acids (e.g., hydroxycarboxy acids), copolymers that compriseacrylic acid or maleic acid, and combinations thereof. One example of asuitable sulfoalkylated lignin comprises a sulfomethylated lignin.Suitable set retarding additives are disclosed in more detail in U.S.Pat. No. Re. 31,190, the entire disclosure of which is incorporatedherein by reference. Suitable set retarding additives are commerciallyavailable from Halliburton Energy Services, Inc. under the trademarksHR® 4, HR® 5, HR® 7, HR® 12, HR®15, HR®25, HR®601, SCR™ 100, and SCR™500 retarders. Generally, where used, the set retarding additive may beincluded in the settable compositions of the present invention in anamount sufficient to provide the desired set retardation. In someembodiments, the set retarding additive may be present in the settablecompositions of the present invention an amount in the range of about0.1% to about 5% by weight of cementitious components. One of ordinaryskill in the art, with the benefit of this disclosure, will recognizethe appropriate amount of the set retarding additive to include for achosen application.

Optionally, other additional additives may be added to the settablecompositions of the present invention as deemed appropriate by oneskilled in the art, with the benefit of this disclosure. Examples ofsuch additives include, but are not limited to, strength-retrogressionadditives, set accelerators, weighting agents, lightweight additives,gas-generating additives, mechanical property enhancing additives,lost-circulation materials, filtration-control additives, dispersants,fluid loss control additives, defoaming agents, foaming agents,oil-swellable particles, water-swellable particles, thixotropicadditives, and combinations thereof. Specific examples of these, andother, additives include crystalline silica, amorphous silica, fumedsilica, salts, fibers, hydratable clays, microspheres, rice husk ash,elastomers, elastomeric particles, resins, latex, combinations thereof,and the like. A person having ordinary skill in the art, with thebenefit of this disclosure, will readily be able to determine the typeand amount of additive useful for a particular application and desiredresult.

As will be appreciated by those of ordinary skill in the art,embodiments of the settable compositions may be used in a variety ofsubterranean applications, including primary and remedial cementing.Embodiments of the settable compositions may be introduced into asubterranean formation and allowed to set therein. For example, thesettable composition may be placed into a space between a subterraneanformation and a conduit located in the subterranean formation.Embodiments of the cement compositions may comprise, for example, waterand one or more of unexpanded perlite, CKD, or pumicite.

In primary cementing embodiments, for example, a settable compositionmay be introduced into a space between a subterranean formation and aconduit (e.g., pipe strings, liners) located in the subterraneanformation. The settable composition may be allowed to set to form anannular sheath of hardened cement in the space between the subterraneanformation and the conduit. Among other things, the set settablecomposition may form a barrier, preventing the migration of fluids inthe well bore. The set settable composition also may, for example,support the conduit in the well bore.

In remedial cementing embodiments, a settable composition may be used,for example, in squeeze-cementing operations or in the placement ofcement plugs. By way of example, the settable composition may be placedin a well bore to plug a void or crack in the formation, in a gravelpack, in the conduit, in the cement sheath, and/or a microannulusbetween the cement sheath and the conduit.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, thescope of the invention.

Example 1

A series of samples were prepared and subjected to 24-hour crushstrength tests in accordance with API Specification 10 to analyze forceresistance properties of settable compositions that comprise unexpandedperlite. The sample compositions were allowed to cure in a water bath atthe temperature indicated in the table below for twenty-four hours.Immediately after removal from the water bath, crush strengths weredetermined using a Tinius Olsen tester. The results of the crushstrength tests are set forth in the table below.

Test Nos. 1-6 were performed on samples with a 14.2 ppg and containingwater, Portland class H cement, ground unexpanded perlite, lime, andwater, as indicated in the table below. The ground unexpanded perlitewas IM-325 from Hess Pumice Products with a particle size of about 325U.S. Standard Mesh.

Test Nos. 7-8 were performed on samples with a density of 14.2 ppg andcontaining water, Portland class H cement, pumicite, and lime, asindicated in the table below. The pumicite was about 200 U.S. StandardMesh in size.

Test Nos. 9-14 were performed on samples with a density of 14.2 ppg andcontaining water, a ground cement/pumicite mixture (FineCem™ 925cement), unexpanded perlite, lime, and water, as indicated in the tablebelow. The ground cement/pumicite mixture comprised Portland Type Vcement (40% by weight) interground with pumicite (60% by weight). Theground cement/pumicite mixture had a mean particle size in the range ofabout 1 to about 4 microns. The ground unexpanded perlite was IM-325from Hess Pumice Products with a particle size of about 325 U.S.Standard Mesh.

In the following table, percent by weight is based on the weight of thePortland cement, cement/pumicite mixture, pumicite, and unexpandedperlite in the sample, and gallons per sack (gal/sk) is based on a94-pound sack of the Portland cement, cement/pumicite mixture, pumicite,and unexpanded perlite.

TABLE 1 Crush Strength Tests Ground Pumicite/ Ground 24-Hr PortlandCement Unexpanded Crush Test Water Cement Mixture Pumicite Perlite LimeTemp. Strength No. (gal/sk) (% by wt) (% by wt) (% by wt) (% by wt) (%by wt) (° F.) (psi) 1 7.44 100 — — — 80 330 2 7.44 100 — — — 140 674 36.74 75 — 25 — 80 290 4 6.74 75 — 25 — 140 777 5 6.95 75 — 25 5 80 352 66.95 75 — 25 5 140 886 7 6.74 75 25 — — 140 835 8 6.95 75 25 — 5 140 7349 6.03 — 100 — — — 80 827 10 6.03 — 100 — — — 140 1877 11 5.68 — 75 — 25— 80 597 12 5.68 — 75 — 25 — 140 2740 13 5.89 — 75 — 25 5 80 530 14 5.89— 75 — 25 5 140 2610

Example 1 thus indicates that replacement of at least a portion of thePortland cement with unexpanded perlite may increase the crush strengthof the settable compositions. At 140° F., for example, the Test Nos. 2and 4 with unexpanded perlite had crush strengths of 886 psi and 777 psias compared to a crush strength of 674 psi for Test No. 1 with 100%Portland cement by weight.

Example 1 further indicates that the ground pumicite/cement mixture incombination with the unexpanded perlite may have synergistic effects onthe settable composition, in that this combination may provide increasedcrush strengths at elevated temperatures. At 140° F., for example, TestNos. 12 and 14 with the ground pumicite/cement mixture and unexpandedperlite had crush strengths of 2740 psi and 2610 psi. This crushstrength is markedly higher than the crush strengths for compositionswith 100% Portland cement (674 psi at 140° F.) and compositions withPortland cement and pumicite that were not ground to fine particle sizes(835 psi and 734 psi at 140° F.). This increased compressive strengthfor combinations of ground pumicite/cement mixture and unexpandedperlite cannot be attributed solely to the addition of expanded perliteas the combination had significantly higher crush strength than seenwith addition of unexpanded perlite to Portland cement (777 psi and 886psi at 140° F.). In addition, this increased compressive strength forcombinations of ground pumicite/cement mixture and unexpanded perlitecannot be attributed solely to the addition of expanded perlite as thecombination had significantly higher crush strength than seen with theground pumicite/cement mixture alone (1877 at 140° F.).

Example 2

An additional series of sample settable compositions were prepared andtested to analyze the force resistance properties of settablecompositions that comprise CKD and unexpanded perlite. The samplecompositions were allowed to cure in a water bath at the temperatureindicated in the table below for either 24 or 72 hours. Immediatelyafter removal from the water bath, crush strengths were determined usinga Tinius Olsen tester. The results of the crush strength tests are setforth in the table below.

Test Nos. 15-28 were performed on samples with a density of 14.2 ppg andcontaining water, CKD, ground unexpanded perlite, and lime, as indicatedin the table below. The samples further contained a cement set retarder(CFR-3™ cement set retarder, Halliburton Energy Services, Inc.) in anamount of about 0.4% by weight. The ground unexpanded perlite was IM-325from Hess Pumice Products with a particle size of about 325 U.S.Standard Mesh.

In the following table, percent by weight is based on the weight of theCKD and unexpanded perlite in the sample, and gallons per sack (gal/sk)is based on a 94-pound sack of the CKD and unexpanded perlite.

TABLE 2 Crush Strength Tests Ground Unexpanded Crush Test Water CKDPerlite Lime Temp. Time Strength No. (gal/sk) (% by wt) (% by wt) (% bywt) (° F.) (Hr) (psi) 15 5.99 100 — — 80 24 21.7 16 5.99 100 — — 140 24267 17 6.19 100 — 5 80 72 173 18 6.19 100 — 5 140 72 457 19 5.65 75 25 —80 24 23.8 20 5.65 75 25 — 140 24 969 21 5.87 75 25 5 80 24 19.6 22 5.8775 25 5 140 24 1004 23 5.5 50 50 5 80 72 124 24 5.5 50 50 5 140 72 119125 5.15 25 75 5 80 72 52 26 5.15 25 75 5 140 72 613 27 4.81 — 100 5 8072 14 28 4.81 — 100 5 140 72 145

Example 2 thus indicates that unexpanded perlite may be used to enhancethe crush strength of CKD-containing compositions. In addition, thiseffect is particularly pronounced at increased temperatures. At 140° F.,for example, Test No. 22 with 75% CKD and 25% unexpanded perlite had a72-hour crush strength of 1004 psi as compared to a 72-hour crushstrength of 457 psi for Test No. 18 with 100% CKD.

Example 3

An additional series of sample settable compositions were prepared andtested to further analyze the force resistance properties of settablecompositions that comprise CKD and unexpanded perlite. The samplecompositions were allowed to cure in a water bath at the temperatureindicated in the table below for 24 hours. Immediately after removalfrom the water bath, crush strengths were determined using a TiniusOlsen tester. The results of the crush strength tests are set forth inthe table below.

Test Nos. 29-37 were performed on samples with a density of 14.2 ppg andcontaining water, CKD, ground unexpanded perlite, and lime, as indicatedin the table below. The samples further contained a cement dispersant inan amount of about 0.4% by weight. The ground unexpanded perlite wasIM-325 from Hess Pumice Products with a particle size of about 325 U.S.Standard Mesh.

In the following table, percent by weight is based on the weight of theCKD and unexpanded perlite in the sample, and gallons per sack (gal/sk)is based on a 94-pound sack of the CKD and unexpanded perlite.

TABLE 3 Crush Strength Tests Ground 24-Hr Unexpanded Crush Test WaterCKD Perlite Lime Temp. Strength No. (gal/sk) (% by wt) (% by wt) (% bywt) (° F.) (psi) 29 6.19 100 — 5 140 278 30 5.48 90 10 — 140 649 31 6.0590 10 5 140 533 32 5.7 80 20 — 140 934 33 5.92 80 20 5 140 958 34 5.4260 40 — 140 986 35 5.64 60 40 5 140 1241 36 5.28 50 50 — 140 897 37 5.550 50 5 140 1197

Example 3 thus indicates that unexpanded perlite may be used to enhancethe crush strength of CKD-containing compositions. For example, asindicated in the table above, the crush strength of the samples steadilyincreased as the concentration of unexpanded perlite in the sample wasincreased from 0% by weight to 40% by weight.

Example 4

An additional series of sample settable compositions were prepared andtested to further analyze the force resistance properties of settablecompositions that comprise CKD and unexpanded perlite. The samplecompositions were allowed to cure in a water bath at the temperatureindicated in the table below for 24 hours. Immediately after removalfrom the water bath, crush strengths were determined using a TiniusOlsen tester. The results of the crush strength tests are set forth inthe table below.

Test Nos. 38-43 were performed on samples with a density of 14.2 ppg andcontaining water, CKD, perlite, and lime, as indicated in the tablebelow. The samples further contained a cement dispersant in an amount ofabout 0.4% by weight. Test Nos. 38 and 39 contained a ground unexpandedperlite (IM-325) from Hess Pumice Products with a particle size of about325 U.S. Standard Mesh. Test Nos. 40 and 41 contained unground perliteore having a mean particle size (d50) of about 190 microns. Test Nos. 42and 43 contained expanded perlite.

In the following table, percent by weight is based on the weight of theCKD and perlite in the sample, and gallons per sack (gal/sk) is based ona 94-pound sack of the CKD and perlite.

TABLE 4 Crush Strength Tests Ground 24-Hr Unexpanded Perlite ExpandedCrush Test Water CKD Perlite Ore Perlite Lime Temp. Strength No.(gal/sk) (% by wt) (% by wt) (% by wt) (% by wt) (% by wt) (° F.) (psi)38 5.65 75 25 — — — 140 969 39 5.87 75 25 — — 5 140 1004  40 5.63 75 —25 — — 140 199 41 5.85 75 — 25 — 5 140 204 42 1.07 75 — — 25 — 140 Notmixable 43 1.29 75 — — 25 5 140 Not mixable

Example 4 thus indicates that unexpanded perlite provides superiorstrength enhancement to CKD-containing compositions when compared tounground perlite ore and expanded perlite. Indeed, the sample with theexpanded perlite could not even be tested due to mixability problems.

Example 5

An additional series of sample settable compositions were prepared andtested to further analyze settable compositions that comprise CKD andunexpanded perlite. The sample compositions were allowed to cure in awater bath at the temperature indicated in the table below for 24 hours.Immediately after removal from the water bath, crush strengths weredetermined using a Tinius Olsen tester. The results of the crushstrength tests are set forth in the table below. The thickening time foreach sample was also determined at 140° F. in accordance with APISpecification 10.

Test Nos. 44-56 were performed on samples with a density of 12.5 ppg andcontaining CKD, perlite, and lime, as indicated in the table below. Thesamples further contained a cement dispersant in an amount of about 0.4%by weight and a cement set retarder (HR® 5 cement retarder, HalliburtonEnergy Services, Inc.). Test Nos. 45, 48, 51, and 54 contained a groundunexpanded perlite (IM-325) from Hess Pumice Products with a particlesize of about 314 U.S. Standard Mesh. Test Nos. 46, 49, 52, and 55contained unground perlite ore having a mean particle size (d50) ofabout 190. Test Nos. 47, 50, 53, and 56 contained expanded perlite.

In the following table, percent by weight is based on the weight of theCKD and perlite in the sample, and gallons per sack (gal/sk) is based ona 94-pound sack of the CKD and perlite.

TABLE 5 Crush Strength and Thickening Time Tests Ground Thick. 24-HrUnexpanded Perlite Expanded Set Time to Crush Test Water CKD Perlite OrePerlite Lime Retarder Temp. 70 Bc Strength No. (gal/sk) (% by wt) (% bywt) (% by wt) (% by wt) (% by wt) (% by wt) (° F.) (psi) (psi) 44 10.51100 — — — 5 0.3 140 4:06 126 45 10.34 90 10 — — 5 0.3 140 4:17 178.2 4610.36 90 — 10 — 5 0.3 140 5:16 119 47 90 — — 10 5 0.6 140 Mixable notpumpable 48 10.18 80 20 — — 5 0.3 140 4:20 311 49 10.18 80 — 20 — 5 0.3140 5:49 100 50 80 — — 20 5 0.3 140 Not mixable 51 9.84 60 40 — — 5 0.3140 5:05 508 52 60 — 40 — 5 0.15 140 9:44 88 53 60 — — 40 5 0.3 140 Notmixable 54 9.67 50 50 — — 5 0.3 140 8:04 616 55 50 — 50 — 5 0 140 23:30 78 56 50 — — 50 5 0.3 140 Not mixable

Example 5 thus indicates that unexpanded perlite provides enhancedstrength to CKD-containing compositions when compared to ungroundperlite ore and expanded perlite. In a similar manner to the precedingexample, the samples with expanded perlite could not even be tested dueto mixability problems.

Example 6

An additional series of sample settable compositions were prepared andtested to further analyze settable compositions that comprise CKD andunexpanded perlite. The sample compositions were allowed to cure in awater bath at the temperature indicated in the table below for 24 hours.Immediately after removal from the water bath, crush strengths weredetermined using a Tinius Olsen tester. The results of the crushstrength tests are set forth in the table below.

Test No. 57 was performed on a sample with a density of 12.5 ppg andcontaining water, Portland Type V cement, CKD, unground perlite ore, andpumicite, as indicated in the table below. The unground perlite ore hada mean particle size (d50) of about 190. The pumicite had a meanparticle size (d50) of about 4 microns.

Test No. 58 was performed on a sample with a density of 12.5 ppg andcontaining water, ground cement/pumicite mixture pumicite, CKD, andground unexpanded perlite. The ground cement/pumicite mixture comprisedPortland Type V cement (40% by weight) interground with pumicite (60% byweight). The ground cement/pumicite mixture had a mean particle size ofabout 1-4 microns. The ground unexpanded perlite was IM-325 from HessPumice Products with a particle size of about 325 U.S. Standard Mesh.

In the following table, percent by weight is based on the weight of theCKD, cement, perlite, pumicite, and/or pumicite/cement mixture in thesample, and gallons per sack (gal/sk) is based on a 94-pound sack of theCKD, cement, perlite, pumicite, and/or pumicite/cement mixture in thesample.

TABLE 6 Crush Strength Tests Ground Portland Pumicite Ground 24-Hr TypeV Cement Unexpanded Perlite Crush Test Water Cement Pumicite Mixture CKDPerlite Ore Temp. Strength No. (gal/sk) (% by wt) (% by wt) (% by wt) (%by wt) (% by wt) (% by wt) (° F.) (psi) 57 9.52 20 30 — 25 — 25 140 20158 9.72 — — 50 25 25 — 140 1086

Example 6 thus indicates that unexpanded perlite in combination withground pumicite provides enhanced strength to CKD-containingcompositions in comparison to compositions with standard cement,pumicite, and unground perlite ore.

It should be understood that the compositions and methods are describedin terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited. Additionally, whenever a numerical range with alower limit and an upper limit is disclosed, any number and any includedrange falling within the range is specifically disclosed. In particular,every range of values (of the form, “from about a to about b,” or,equivalently, “from approximately a to b,” or, equivalently, “fromapproximately a-b”) disclosed herein is to be understood to set forthevery number and range encompassed within the broader range of valueseven if not explicitly recite. Thus, every point or individual value mayserve as its own lower or upper limit combined with any other point orindividual value or any other lower or upper limit, to recite a rangenot explicitly recited.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Although individual embodiments arediscussed, the invention covers all combinations of all thoseembodiments. Furthermore, no limitations are intended to the details ofconstruction or design herein shown, other than as described in theclaims below. Also, the terms in the claims have their plain, ordinarymeaning unless otherwise explicitly and clearly defined by the patentee.It is therefore evident that the particular illustrative embodimentsdisclosed above may be altered or modified and all such variations areconsidered within the scope and spirit of the present invention.

What is claimed is:
 1. A subterranean formation settable compositioncomprising: ground unexpanded perlite; Portland cement interground withpumicite; and water present in an amount sufficient to form a pumpableslurry.
 2. The composition of claim 1 wherein the settable compositionhas a density in the range of about 8 pounds per gallon to about 16pounds per gallon.
 3. The composition of claim 1 wherein the groundunexpanded perlite has a mean particle size in the range of about 1micron to about 400 microns.
 4. The composition of claim 1 wherein theground unexpanded perlite has a mean particle size in the range of about1 micron to about 100 microns.
 5. The composition of claim 1 wherein theground unexpanded perlite is present in an amount in the range of about1% to about 75% by weight of cementitious components in the settablecomposition.
 6. The composition of claim 1 wherein the water is selectedfrom the group consisting of freshwater, saltwater, brine, seawater, andany combination thereof.
 7. The composition of claim 1 wherein the wateris present in an amount in the range of about 40% to about 200% byweight of cementitious components in the settable composition.
 8. Thecomposition of claim 1 wherein the Portland cement interground withpumicite has a mean particle size in the range of about 0.5 microns toabout 50 microns.
 9. The composition of claim 1 wherein the settablecomposition further comprises lime.
 10. The composition of claim 1wherein the settable composition further comprises at least one additiveselected from the group consisting of fly ash, slag cement, metakaolin,shale, zeolite, crystalline silica, amorphous silica, fumed silica,salt, fiber, hydratable clay, microsphere, rice husk ash, elastomericparticle, resin, latex, and any combination thereof.
 11. The compositionof claim 1 wherein the settable composition further comprises at leastone additive selected from the group consisting of a set retardingadditive, a strength-retrogression additive, a set accelerator, aweighting agent, a lightweight additive, a gas-generating additive, amechanical property enhancing additive, a lost-circulation material, afiltration-control additive, a dispersant, a fluid loss controladditive, a defoaming agent, a foaming agent, an oil-swellable particle,a water-swellable particle, a thixotropic additive, and any combinationthereof.
 12. A subterranean formation settable composition comprising:ground unexpanded perlite present in an amount in the range of about 1%to about 75% by weight of cementitious components in the settablecomposition; Portland cement interground with pumicite, wherein thePortland cement interground with pumicite has a mean particle size inthe range of about 0.5 microns to about 50 microns; and water present inan amount sufficient to form a pumpable slurry.
 13. The composition ofclaim 12 wherein the settable composition has a density in the range ofabout 8 pounds per gallon to about 16 pounds per gallon.
 14. Thecomposition of claim 12 wherein the ground unexpanded perlite has a meanparticle size in the range of about 1 micron to about 400 microns. 15.The composition of claim 12 wherein the ground unexpanded perlite has amean particle size in the range of about 1 micron to about 100 microns.16. The composition of claim 12 wherein the water is selected from thegroup consisting of freshwater, saltwater, brine, seawater, and anycombination thereof and is present in an amount in the range of about40% to about 200% by weight of cementitious components in the settablecomposition.
 17. The composition of claim 12 wherein the settablecomposition further comprises at least one additive selected from thegroup consisting of fly ash, slag cement, metakaolin, shale, zeolite,crystalline silica, amorphous silica, fumed silica, salt, fiber,hydratable clay, microsphere, rice husk ash, elastomeric particle,resin, latex, cement kiln dust, and any combination thereof.
 18. Thecomposition of claim 12 wherein the settable composition furthercomprises at least one additive selected from the group consisting of aset retarding additive, a strength-retrogression additive, a setaccelerator, a weighting agent, a lightweight additive, a gas-generatingadditive, a mechanical property enhancing additive, a lost-circulationmaterial, a filtration-control additive, a dispersant, a fluid losscontrol additive, a defoaming agent, a foaming agent, an oil-swellableparticle, a water-swellable particle, a thixotropic additive, and anycombination thereof.
 19. A subterranean formation settable compositioncomprising: ground unexpanded perlite; Portland cement interground withpumicite; at least one additive selected from the group consisting of aset retarding additive, a strength-retrogression additive, a setaccelerator, a weighting agent, a lightweight additive, a gas-generatingadditive, a mechanical property enhancing additive, a lost-circulationmaterial, a filtration-control additive, a dispersant, a fluid losscontrol additive, a defoaming agent, a foaming agent, an oil-swellableparticle, a water-swellable particle, a thixotropic additive, and anycombination thereof; and water present in an amount in the range ofabout 40% to about 200% by weight of cementitious components in thesettable composition, and wherein the water is present in an amountsufficient to form a pumpable slurry.
 20. The settable composition ofclaim 19 wherein: the ground unexpanded perlite has a mean particle sizein the range of about 1 micron to about 400 microns and is present in anamount in the range of about 1% to about 75% by weight of cementitiouscomponents in the settable composition, and the Portland cementinterground with pumicite has a mean particle size in the range of about0.5 microns to about 50 microns.